Patent Application
20120140936
Embodiments relate to monitoring sound quality from one or more loudspeakers and compensating, if needed, audio signals to be outputted on the loudspeakers, and more particularly relate to compensating signals based on a signature response of a loudspeaker to a test signal and a subsequent response of the loudspeaker to the test signal.
The cinema industry continues to become more competitive. In view of such competition, the trend is to automate as much of the sequencing of the cinematic presentation process as possible to reduce costs. The cinematic presentation includes a sound component and a visual component that are properly sequenced with respect to each other. With the emergence of digital projection and sound systems in theatres it has become easier to automate the cinematic presentation sequencing using computer-controlled show automation systems such that staff is not required to set-up the projector and sound system each time the presentation is run. Accordingly, the presentation quality (e.g. the sound and visual performance) may be monitored less frequently.
For organizations that take pride to ensure the theatre patron is provided the best show experience possible, quality problems can be an ongoing concern. In particular the sound quality problems associated with the degradation of the sound system can result in the sound not meeting the quality sound expected by the theatre patron and can reduce the experience of a premium presentation.
Cinema loudspeaker systems need to perform reliably for extended periods. This is in conflict with the natural changes in the loudspeaker characteristics due to aging or changing environmental conditions, such as temperature and humidity. These natural changes, among other changing performance characteristics, are a typical problem that occurs over time. Other potential performance issues include (i) one driver in a cluster of drivers within a loudspeaker fails or is experiencing a degradation because of a loose connection or otherwise; (ii) a fuse blows, leaving inoperable the mid-range driver(s) or high range driver(s); and (iii) audio amplifier degradation or failures to degraded sound in the theatre. One approach to recognize one or more of these deficiencies is to repeat a theatre sound system tuning test to determine a performance deficiency.
Additionally, the acoustics of the theatre hall can change depending on the number of viewing patrons present (i.e. acoustics can be different if the theatre is full than if the theatre is nearly empty) and the location within the hall of where the patrons are seated. If the acoustics of the hall has changed, causing a reduction in sound quality, adjustments to the equalization of the sound system may be required to compensate for the change.
Typically initial tuning of the sound system is performed during theatre sound system installations in which the performance of the sound system setup is measured and calibrated using a microphone. Measuring with the microphone is performed at various seat positions in the theatre to ensure the sound for most if not all seat locations are optimized. Unfortunately, the setup used for calibration does not lend itself to be used as a sound system monitoring setup. This is partially because patrons are in theatre seats during the monitoring (but not during tuning), which ultimately influences the ability of such a setup to be used effectively for monitoring loudspeaker performance. To effectively monitor the sound quality, a microphone is placed a distance away from theatre patrons but still within the sound dispersion profile. This limits locations for monitoring microphone placement. For example, placing a microphone ten feet above a seating patron's head position and outside of the projected image path may potentially place the microphone outside of the sound dispersion profile. Thus, the placement may not be an effective position for sound quality monitoring. Furthermore, temporarily lowering a microphone into position when the patrons are seated is an added element of complication that increases the expense of a monitoring system.
Alternatively, the performance of the loudspeakers can be evaluated during periodic inspections, but this process is time consuming and does not identify problems when the problems occur. For example, periodic inspection does not provide any remedy or compensation for changes in acoustical performance until service can be arranged. As with the installation calibration setup, trained personnel is needed to perform measurements properly in monitoring on a periodic basis, thus making this approach less attractive economically (among other reasons).
In addition, the acoustical effects of nearby surfaces can alter the acoustical transfer characteristics of the microphone significantly if the microphones are placed in sub-optimal (e.g. non-ideal) locations. If measurements are made from these locations without otherwise compensating for the complex interactions that occur (and assuming the measurement hardware has a flat response), the correction applied to the loudspeaker response may be distorted by the acoustics of the microphone location. Accordingly, sub-optimal microphone placement is generally avoided.
The acoustical interaction may be too complex to approximate with a simple weighting filter unique to each microphone in each theatre. Discrepancies between the actual acoustical transfer function and an approximated weighting filter may be interpreted by the measurement system as an error to be corrected. This is undesirable as the loudspeaker response can be corrected to compensate for the microphone response rather than the opposite.
Accordingly, systems and methods for theatre sound quality monitoring are desirable that can be implemented using microphones placed in a variety of positions, including sub-optimal positions. Systems and methods are also desirable that can monitor for theatre sound quality effectively to compensate quality problems automatically. Systems and methods are also desirable that can identify larger issues with a theatre sound system and notify theatre operators regarding those larger issues.
In at least one aspect, a method is described for compensating for changes in a theatre sound system that is positioned in a theatre. A difference between a signature response of a loudspeaker to a test signal and a subsequent response of the loudspeaker to the test signal is determined. The subsequent response of the loudspeaker is subsequent to the signature response of the loudspeaker. The loudspeaker is in the theatre sound system. The signature response and the subsequent response are captured by a microphone at a suboptimal position in the theatre. An audio signal is modified by an equalizer unit based on the difference to generate a compensated audio signal. The compensated audio signal is outputted to the loudspeaker.
In at least one embodiment, the audio signal is modified based on the difference to generate the compensated audio signal by determining an inverse of the difference and convolving the inverse of the difference with the audio signal.
In at least one embodiment, the difference between the signature response and the subsequent response is determined by determining an inverse of the signature response. The inverse of the signature response is used to determine a correction to linearize the signature response to a predetermined limit. The correction is applied to the subsequent response to generate a corrected response. The corrected response is compared to the predetermined limit to determine the difference. The difference represents an amount by which to linearize the corrected response to the predetermined limit.
In at least one embodiment, the test signal includes audio of at least one frequency in a hearing range of a human.
In at least one embodiment, the test signal includes at least one of an impulse signal, a chirp signal, a maximum length sequence signal, or a swept sine signal.
In at least one embodiment, a microphone positioned at a suboptimal position in the theatre captures the subsequent response of the loudspeaker to the test signal.
In at least one embodiment, the subsequent response of the loudspeaker to the test signal is captured by capturing the subsequent response when at least one person is located in the theatre.
In at least one embodiment, the microphone positioned at the suboptimal position captures the signature response of the loudspeaker to the test signal prior to capturing the subsequent response of the loudspeaker to the test signal.
In at least one embodiment, the theatre sound system is tuned prior to determining the difference.
In at least one embodiment, the differences are determined and the motion picture audio signals are modified based on the differences, periodically.
In another aspect, a system is provided that is capable of compensating for changes in performance of a theatre sound system that is positioned in a theatre. The system includes an equalizer unit. The equalizer unit can receive a signature response of a loudspeaker to a test signal and receive a subsequent response of the loudspeaker to the test signal. The equalizer unit can modify an audio signal using a difference between the signature response and the subsequent response and can output to the loudspeaker the audio signal modified based on the difference. The equalizer unit is capable of determining the difference.
In at least one embodiment, the system includes an audio processing device that includes a playback device, an audio processor, an amplifier, and a user console. The playback device can source the audio signal. The audio processor can synchronize and process the audio signal. The amplifier can drive the loudspeaker. The user console can allow a user to control the playback device and the audio processor. The equalizer unit can generate the test signal.
In at least one embodiment, the equalizer unit can, in response to determining the subsequent response is between predetermined low limits, output to the loudspeaker the audio signal without being modified based on the difference. The equalizer unit can, in response to determining the subsequent response exceeds a predetermined high limit, output a notification to a user interface for a theatre operator without modifying the audio signal based on the difference. The equalizer unit can modify the audio signal based on the difference and output to the loudspeaker the audio signal modified based on the difference, in response to determining the subsequent response is between at least one predetermined low limit and at least one predetermined high limit.
In another aspect, a theatre sound system is described. The system includes a loudspeaker, a microphone, and an audio device. The loudspeaker is positioned in an auditorium. The microphone is positioned in a suboptimal location in the auditorium and within an audio dispersion path associated with the loudspeaker. The microphone can capture a signature response and a subsequent response of the loudspeaker to a test signal. The audio device can generate a difference between the signature response and the subsequent response and can modify an audio signal of a motion picture based on the difference to generate a compensated signal that is capable of compensating for changes causing degradation of sound quality in the loudspeaker since the signature response.
These illustrative aspects and embodiments are mentioned not to limit or define the invention, but to provide examples to aid understanding of the inventive concepts disclosed in this application. Other aspects, advantages, and features of the present invention will become apparent after review of the entire application.
a is a chart illustrating a signature response and predetermined limits according to one embodiment of the present invention.
b is a chart illustrating a subsequent response and predetermined limits according to one embodiment of the present invention.
c is a chart illustrating a difference between a subsequent response and a signature response according to one embodiment of the present invention.
d is a chart illustrating an inverse of the difference from
a is a chart illustrating a signature response according to one embodiment of the present invention.
b is a chart illustrating a linearized signature response according to one embodiment of the present invention.
c is a chart illustrating a subsequent response according to one embodiment of the present invention.
d is a chart illustrating a subsequent response and predetermined limits according to one embodiment of the present invention.
e is a chart illustrating a linearized subsequent response according to one embodiment of the present invention.
Certain aspects and embodiments relate to a theatre sound quality monitoring system. In one embodiment, the system is capable of receiving signals from quality monitoring microphones positioned at sub-optimal positions. The system can be “taught” a signature response of the loudspeaker to a test signal as measured through one or more of the quality monitoring microphones after the theatre sound system is tuned using tuning microphones placed at optimal locations. The signature response can have localized acoustical effects incorporated into the microphone's measurement of the test signal. Subsequent measurements of the loudspeaker's response to the test signal can include the same localized acoustical effects. The localized acoustics can be fixed due to the walls, floor, ceiling and screen, along with the microphone and the loudspeaker, not changing position. Other effects can change due to one or more variables and those effects can be identified.
For example, both the signature response and the subsequent response can include an acoustical transfer function associated with the microphone location. The portion of the response influenced by the acoustical transfer function in both measurements is subtracted out when the subsequent response is subtracted from the signature response to determine a difference. The difference may represent an error or otherwise a change that the system can identify and correct.
In some embodiments, the difference between the signature response and the subsequent response is analyzed. If the difference is sufficient, such as by being above a predetermined limit, the system can perform adjustments to equalization settings that control frequency profile of the audio channel to the loudspeaker so that the loudspeaker's response to the test signal can be corrected. This may be performed for each loudspeaker in the theatre such that the theatre sound system can perform within acceptable limits. This may be performed prior to each presentation to allow for a more immediate response to an acoustical quality problem. If the sound quality problem can be corrected by making audio signal equalization adjustments, then the compensation can be applied prior to each show. These adjustments may not be possible in normally scheduled sound system service routines, which are often performed once or twice a year.
In some embodiments, a needed adjustment to correct a loudspeaker response that exceeds a second predefined limit is electronically flagged and a notification regarding the adjustment is provided to a system operator or other appropriate personnel by electronic means.
In some embodiments, quality checks of the theatre sound system are performed by the system periodically, such as on a per show basis, a daily routine.
A selected number of microphones can be placed in the presentation hall to monitor the sound system quality. The microphones can be placed within an appropriate portion of the sound dispersion pattern of each loudspeaker to, for example, avoid interfering with the patron's view of the presentation. Any number of microphones can be used. In a theatre hall with a loudspeaker distribution described above, three microphones can be used for quality monitoring of the sound system. One microphone 122 can be located along the back wall such that it is within a dispersion pattern of the loudspeakers behind the screen, allowing sound from these loudspeakers to be monitored. To monitor the sound from the loudspeakers positioned near or at the rear of the theatre, two microphones 126, 128 can be positioned along one or more theatre side walls in line with the direction of each respective rear loudspeaker's sound dispersion pattern. The sub-bass loudspeaker 140 can have omni-directional dispersion characteristics such that any one or more of the monitoring microphones 122, 126, 128 can be used to monitor the sub-bass loudspeaker 140.
The sound dispersion pattern of cinema loudspeakers can be broad to ensure best coverage over the audience seat locations. Given this spatially controlled directivity of the sound, the microphones can be positioned in locations within a defined area as outlined by the dotted lines emanating from each loudspeaker position shown in
Systems according to various embodiments of the present invention can include any configuration that can identify sound quality issues in a theatre sound system and to compensate for at least some of the identified sound quality issues. In some embodiments, the system includes an audio device that implements methods according to various embodiments of the present invention using hardware, software stored on a computer-readable medium, or a combination of hardware and software.
Audio devices can include one or more components or functional components.
In the sound system configuration of theatre hall 100, at least five audio channels and one sub-bass channel can be present. The equalizer unit 314 can modify the audio signal to each of the loudspeakers for tuning to optimize the sound in the theatre hall for patrons. Quality monitoring can include providing information from the quality monitoring microphones 122, 126, 128 to the equalizer unit 314. The equalizer unit 314 can send a test signal, receive loudspeaker responses from the microphones, process the received responses and compensate the audio signal based on processed information, such as a difference based on a signature response of a loudspeaker to a test signal and a subsequent response of the loudspeaker to the test signal.
Tuning components, such as a tuning microphone 330 and a tuning computer 332, can be integrated with the system 300. The tuning computer 332 can be a general purpose computer that has been configured to execute a tuning software program stored on a computer-readable medium. The tuning components can be integrated permanently or temporally, as indicated via the dashed lines in
Before the tuning begins, the theatre hall can be set-up, such as by being configured in a finished condition. A finished condition can include installing elements affecting room acoustics. Examples of these elements include seats, sound absorbing materials, a screen, carpet or other flooring, doors and booth window, and loudspeakers. The elements may be aligned for optimal sound dispersion.
Tuning the theatre sound system can include positioning the tuning microphone 330 at various seat locations while a tuning test signal, programmed within a tuner device such as a tuning computer 332, is applied to one or more of the loudspeakers 318 by the equalizer unit 314. By applying the tuning test signal, the tuning computer 332 can determine optimal tuning parameter settings. Tuning can be used to create an ideal or flat response of a theatre sound system at optimal microphone locations, which correspond to patron seat locations. Tuning parameters can include adjusting a frequency profile and volume levels to the audio channels for each of the loudspeakers 318 to produce an optimal and consistent sound quality over the viewing patron seat locations. At the time of tuning, patrons are absent from seats. In some implementations, the amount of time needed to tune a theatre sound system can be completed in one or two days, or hours, to achieve optimum performance. The tuning process can include multiple measurements and require a professional to interpret the results to make the necessary sound system adjustments. The tuning process also includes placing the microphones at ideal locations, which would be in the field of view of the presentation image if an audience were present. Typically after the tuning is complete the tuning computer 332 and the tuning microphone 330 are removed.
In block 406, the equalizer unit 314 provides a test signal to a loudspeaker. One or more microphones can capture the loudspeaker's response to the test signal as a signature response and provide the signature response to the equalizer unit 314. In a theatre hall configured as in
Even though the quality monitoring microphones can be placed in less than ideal locations, they may be appropriately placed to obtain a useful response. For example, because of the suboptimal positioning, the response obtained through the quality monitoring microphones may not have an optimal profile, but the response can indicate what the profile should be at the location of the microphone for a particular loudspeaker of the optimally tuned sound system. The response obtained from the quality monitoring microphones to the test signal just after the theatre sound system is tuned may be a reference signature response. Signature responses captured via a monitoring microphone according to various embodiments are non-ideal and non-flat signals, which are different than signals obtained via optimally placed tuning microphones.
In some embodiments, a signature response can be obtained for each loudspeaker and the signature responses can be recorded. The equalizer unit 314 can store each signature response such that the theatre sound quality monitoring system can be “taught” the signature response of each loudspeaker. Teaching signature responses can be implemented irrespective of periods of time. After being “taught” the signature response, the system can periodically monitor responses and compensate accordingly as explained below.
In block 408, a signature response is captured. The signature response is a response to the test signal by a loudspeaker that can be used as a benchmark to compare to responses captured subsequently.
A quality monitoring process according to some embodiments can include determining if changes have occurred at some later time in the theatre sound system loudspeaker response. In block 410, the test signal is provided to a loudspeaker and a subsequent response to the test signal is captured. In some embodiments, a set of subsequent responses for each loudspeaker is obtained.
The subsequent measurements can be made at the beginning or end of a day of presentations, or before each presentation. In one embodiment, the subsequent responses are captured with patrons absent from the theatre. In another embodiment, subsequent responses are captured with the patrons present in the theatre prior to the start of the presentation. For example, the theatre sound quality monitoring system can account for patrons influencing the acoustic response of the monitoring microphones. Certain embodiments of the quality monitoring system can compensate for differences between a full and partially full theatre.
In some embodiments, the type of test signal can determine whether the subsequent response is made with the audience in the theatre. For example, noise produced from the loudspeakers may startle or annoy the audience if an impulse is used. Using a different type of test signal may be more acceptable if doing the subsequent measurement while the audience is present.
In block 412, the equalizer unit 314 compares the subsequent response to predetermined limits to determine whether the system can automatically compensate for the response of the loudspeaker. The predetermined limits can be determined as offsets to the signature response. Examples of predetermined limits are depicted in
By comparing the subsequent response to the predetermined limits, the frequencies that have been attenuated or emphasized can be determined. For example, if the attenuation or emphasis of certain frequencies is determined to be minimal by predetermined lower limits, then the audio signal can be outputted without compensating for loudspeaker performance changes and the quality monitoring at least for that time and for that loudspeaker ends in block 414. Dashed lines 621, 623 in
If comparing the subsequent response to the predetermined limits results in exceeding a predetermined high limit, then the system can output a notification in block 416 to an operator or otherwise that notifies the operator of the issue to be addressed by the operator or by other means. Examples of such issues include a non-functional loudspeaker or an audio system component that causes the discrepancy.
If comparing the subsequent response to the predetermined limits results in at least part of the subsequent response being between a lower limit and a higher limit, the process proceeds to block 418 to determine compensation for an audio signal.
In block 418, the equalizer unit 314 determines a difference between the signature response and the subsequent response.
In block 420, the equalizer unit 314 determines an inverse of the difference.
In block 422, the equalizer unit convolves at least part of the inverse of the difference with an audio signal to generate a compensated signal for the loud speaker. In some embodiments, the inverse of the difference is convolved with the audio signal using a digital Finite Impulse Response (FIR) filter. The FIR filter response can be represented by a series summation that has a finite number of terms. Each term in the summation has a filter coefficient. The inverse of the difference of the subsequent response with respect to the signature response can be represented as a series summation where each term has a coefficient. The inverse of the difference is the response desired from the filter. Thus, the coefficients in the series summation for the inverse of the difference can be the filter coefficients. The FIR filter modifies the audio signal based on filter coefficients that can be determined based on the difference. If the test signal is an impulse signal, the difference can be in the time domain. This can represent the inverse of the difference and when convolved with the input audio signal the output signal is the compensated signal to the loudspeakers. To convolve the inverse of the difference with the input audio signal using the FIR filter, the coefficients that control the FIR filter can be determined from the difference.
An impulse test signal is one example of a test signal. Other types of test signals can be used and a compensated signal can be constructed based on the difference between the subsequent response and the signature response. Computations to complete the construction of the compensated signal can be relatively complicated. Other types of equalizer units (e.g. units with infinite impulse response (IIR) filters or analogue filters) that perform equalization by methods with which it is possible to adapt compensation of the audio signal based on the difference between a subsequent response and the signature response for the specific test signal.
In some embodiments, a match of the corrected response for each loudspeaker with its reference signature can be confirmed using the same process outlined above. If there is a difference to be corrected, the new difference can be used to adjust the coefficients of the FIR filter. For example, the process can be used to confirm the compensated audio signal.
The compensated signal can be provided to the loudspeaker for output to theatre patrons.
In block 500, a test signal is provided to a loudspeaker. In block 502, a signature response of the loudspeaker to the test signal is captured. These processes are similar to those in blocks 406 and 408 of
In block 504, the equalizer unit 314 determines an inverse of the signature response and uses the inverse to determine a correction to linearize the signature response to a predetermined limit.
In block 506, the equalizer unit 314 provides the test signal to the loudspeaker, and a subsequent response of the speaker to the test signal is captured.
In block 508, the equalizer unit 314 applies the correction to the subsequent response to generate a corrected subsequent response. In some embodiments, the correction is represented by coefficients that control the FIR filter in the equalizer unit 314 that is used to process the subsequent response.
In block 510, the equalizer unit 314 compares the corrected subsequent response to predetermined limits.
If the corrected subsequent response is between one of the low limits 721, 723 and one of the high limits 725, 727, the equalizer unit 314 in block 512 determines a difference that is a subsequent correction to linearize the subsequent response to between the low limits 721, 723.
In block 514, the equalizer unit 314 applies the difference to an audio signal to generate a compensated audio signal. In some embodiments, equalizer unit uses the difference to adjust filter coefficients of the filter applied to the audio signal to compensate the audio signal. The compensated audio signal can be provided to the loudspeaker for output to theatre patrons.
Processes according to various embodiments of the present invention can be configured to monitor sound quality automatically. This can allow sound quality monitoring to be tied into a cinema's automated show routine to perform sound quality checks automatically and on a routine basis. With this process, compensation for gradual sound system degradation can be performed in an automated way or failed sound system channels can be flagged automatically for immediate action.
Compensation processes according to various embodiments can be completed on those portions of the subsequent response that exceed the first set of low limits, but not the second set of high limits, or the compensation processes can be completed on the whole subsequent response when a portion of the subsequent response exceeds the first, set of limits, but not the second set of limits.
Various methods and processes can be used to determine coefficients for the equalizer filters in accordance with accepted techniques associated with digital filter design. “Advanced Digital Audio” by Ken C. Pohlmann, SAMS (1991), specifically Chapter 10, discloses examples of convolving and processing using digital filters.
The foregoing description of the embodiments, including illustrated embodiments, of the invention has been presented only for the purpose of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to those skilled in the art without departing from the scope of this invention.
This application claims the benefit of U.S. Provisional Application No. 61/230,833, filed Aug. 3, 2009 and entitled “Systems and Methods for Monitoring Cinema Loudspeakers and Correcting Quality Problems,” the contents of which are incorporated herein by this reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2010/001920 | 8/3/2010 | WO | 00 | 2/1/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61230833 | Aug 2009 | US |
